Anchor member locking features

Abstract

An implantable medical device may include an implant member having an aperture extending therethrough. An anchor member may be configured to extend through the aperture. A locking ring may be supplied to inhibit back-out of the anchor member.

We claim: 
     
       1. An implantable medical device, comprising:
 an implant member having an upper surface configured to interface with a bone structure, a lower surface configured to interface with a bone structure, and a side surface extending from the upper surface to the lower surface, the implant member also having an angled aperture extending through the side surface, the aperture having an axis and having an inner surface with a semicircular channel formed in the inner surface, the channel being disposed in a plane substantially normal to the axis and disposed at a depth within the angled aperture where the plane intersects with the inner surface along a partial circumferential line and not a complete circumferential line, the semicircular channel being formed by first and second sidewalls and end boundary walls, the end boundary walls forming ends of the channel and being disposed on substantially opposing sides of the aperture; and 
 a semicircular locking ring disposed in the semi-circular channel and being sized to extend about to the end boundary walls of the channel, the locking ring having an upper surface and a lower surface, the upper surface being disposed to face the first side wall of the channel and the lower surface being disposed to face the second sidewall of the channel, wherein the end boundary walls are configured to limit rotation of the locking ring in the semicircular channel, the locking ring being configured to cooperate with the implant member to prevent back-out of an anchor member in the aperture. 
 
     
     
       2. The device of  claim 1 , further comprising:
 an anchor member configured to extend through the aperture, the anchor member having a geometry that interacts with the locking ring to expand the locking ring while inserting the anchor member. 
 
     
     
       3. The device of  claim 1 , wherein the ring is elastically deformable in a manner that allows an anchor member to pass in a first direction and restrict passage in an opposite second direction. 
     
     
       4. The device of  claim 1 , wherein the channel includes a first portion having a first depth and a slot formed therein having a second depth different than the first depth, and wherein the ring includes a protruding portion configured to fit within the slot. 
     
     
       5. The device of  claim 4 , wherein the locking ring includes a first and a second end, the protruding portion being a first protruding portion at the first end and further including a second protruding portion at the second end. 
     
     
       6. The device of  claim 1 , wherein the locking ring has a first inner diameter while in a neutral condition, the device comprising an anchor member including a head portion having a second diameter greater than the first diameter of the locking ring. 
     
     
       7. The device of  claim 1 , wherein the channel is disposed within the aperture so that a cross-section through the inner surface intersects only a part of the inner surface. 
     
     
       8. The device of  claim 1 , wherein the locking ring is entirely contained within the aperture. 
     
     
       9. The device of  claim 1 , wherein the implant member is a spacer sized for placement between adjacent vertebrae. 
     
     
       10. The device of  claim 9 , wherein the aperture is aligned in the implant member so that an anchor member in the aperture is aligned to penetrate a bearing surface of a vertebral body. 
     
     
       11. The device of  claim 1 , wherein the implant member and the locking ring are configured to fit entirely within the disc space. 
     
     
       12. An implantable medical device, comprising:
 an implant member having a front surface, upper and lower bearing surfaces, and an aperture extending through the front surface toward one of the upper and lower bearing surfaces, the aperture having an axis and having an inner surface and having a channel formed in the inner surface, the channel being disposed in a plane substantially normal to the axis and disposed at a depth within the aperture where the plane intersects with the inner surface along a partial circumferential line and not a complete circumferential line, the implant having at least one radially projecting slot in the channel; and 
 a locking ring disposed in the channel, the locking ring having at least one protruding portion that extends into the radially projecting slot, the locking ring being configured to cooperate with the implant member to prevent back-out of a bone screw in the aperture. 
 
     
     
       13. The device of  claim 12 , wherein the slots are sized to permit the locking ring to expand within the channel. 
     
     
       14. The device of  claim 12 , wherein the channel and the locking ring are semi-circular. 
     
     
       15. The device of  claim 12 , further comprising:
 an anchor member configured to extend through the aperture, the anchor member having a geometry that interacts with the locking ring to expand the locking ring while inserting the anchor member. 
 
     
     
       16. The device of  claim 12 , wherein the ring is elastically deformable in a manner that allows an anchor member to pass in a first direction and restrict passage in an opposite second direction. 
     
     
       17. The device of  claim 12 , wherein the locking ring includes a first and a second end, the protruding portion being a first protruding portion at the first end and further including a second protruding portion at the second end. 
     
     
       18. An implantable medical device, comprising:
 an implant member having an upper surface configured to interface with a bone structure, a lower surface configured to interface with a bone structure, and a side surface extending from the upper surface to the lower surface, the implant member also having an angled aperture extending through the side surface, the aperture having an axis and having an inner surface with a semicircular channel formed in the inner surface, the channel being disposed in a plane substantially normal to the axis and disposed at a depth within the angled aperture where the plane intersects with the inner surface along a partial circumferential line and not a complete circumferential line, the channel having a first end and a second end, the first and second ends being located on substantially opposing sides of the aperture, each of the first and second ends forming boundary walls, the channel including a channel bottom surface, and including slots formed in the channel bottom surface at the first and second ends, the slots extending radially outward from the channel bottom surface to have a depth greater than the depth of the channel bottom surface; 
 a semicircular locking ring extending substantially from the first end of the channel to the second end of the channel, at least a portion of the locking ring being disposed within the channel and at least a portion of the locking ring being disposed outside the channel in the aperture, the locking ring having first and second ends that outwardly protrude and fit within the slots in the channel, the locking ring being configured to cooperate with the implant member to prevent back-out of an anchor member in the aperture; and 
 an anchor member configured to extend through the aperture, the anchor member having a geometry that interacts with the locking ring to expand the locking ring so that the first and second ends of the locking ring protrude more deeply into the respective first and second slots while inserting the anchor member. 
 
     
     
       19. The device of  claim 18 , wherein the ring is elastically deformable in a manner that allows an anchor member to pass in a first direction and restrict passage in an opposite second direction. 
     
     
       20. The device of  claim 18 , wherein the locking ring has a first inner diameter while in a neutral condition, the anchor member including a head portion having a second diameter greater than the first diameter of the locking ring. 
     
     
       21. The device of  claim 18 , wherein the channel is disposed within the aperture so that a cross-section through the inner surface intersects only a part of the inner surface. 
     
     
       22. The device of  claim 18 , wherein the implant member is a spacer sized for placement between adjacent vertebrae. 
     
     
       23. The device of  claim 18 , wherein the aperture is aligned in the implant member so that an anchor member in the aperture is aligned to penetrate a bearing surface of a vertebral body. 
     
     
       24. The device of  claim 18 , wherein the implant member and the locking ring are configured to fit entirely within the disc space. 
     
     
       25. The device of  claim 18 , wherein the locking ring includes a planar upper surface and a parallel planar lower surface.